In a manufacturing process of electronic devices such as semiconductor devices, plasma processing may be performed on a target object to be processed by using a plasma processing apparatus. The plasma process includes plasma etching. The plasma etching is performed to transfer a pattern of a mask formed on an etching target layer to the etching target layer. As for the mask, a resist mask is generally used. The resist mask is formed by a photolithography technology. Therefore, a limit of dimension of the pattern formed on the etching target layer depends on resolution of the resist mask formed by the photolithography technology. However, the resolution of the resist mask has a resolution limit. Since the demand for high integration of the electronic devices is increasing and the formation of a pattern having a dimension smaller than the resolution limit of the resist mask is required, there is suggested in Japanese Patent Application Publication No. 2004-80033 a technique for adjusting a dimension of a resist mask by forming a silicon oxide film on the resist mask and reducing a width of an opening provided by the resist mask.
Due to the recent trend toward miniaturization accompanying the high integration of the electronic devices, it is required to control a critical dimension (CD) with high accuracy in forming a pattern on the target object. Further, a long-term stable reproducibility of the critical dimension or the like is required in view of a production yield of the electronic devices.
In the plasma processing, the critical dimension generally varies due to changes in the plasma state caused by changes in surface states of constituent components (e.g., an inner wall surface of a processing chamber where the plasma is generated, inner wall surfaces of various lines connected to the processing chamber, and the like) of the plasma processing apparatus, which are exposed to a processing space where a plasma is generated. The surface states of the constituent components of the plasma processing apparatus which are exposed to the processing space are changed by consumption of the surfaces of the corresponding components due to long-term use of the plasma. The consumption of the surfaces of the corresponding components leads to changes in surface temperatures of the corresponding components. The changes in the surface temperatures result in changes in a deposition rate of radicals.
Further, in the plasma processing, particles that may cause product defects may be generated. The particles may be generated from the surfaces of the constituent components of the plasma processing apparatus which are exposed to the processing space. The adhesion of the particles on a wafer leads to product failure. If the particles are adhered onto the pattern, the transfer of the pattern is disturbed and, further, the realization of the critical dimension with high accuracy and the stable reproduction of the critical dimension may be disturbed.